dict = {"k1":"v1","k2":"v2","k3":"v3"}
#1、请循环遍历出所有的key
for i in dict:
    print(i)

#2、请循环遍历出所有的value
for k in dict.values():
    print(k)

# 3、请在字典中增加一个键值对,"k4":"v4"
dict["k4"] = "v4"
# print(dict)